Melt chocolate over a double boiler. Whip the cream till it starts to thicken. Gradually add melted chocolate while whisking the cream.
Break the meringue into pieces. Fold into the cream mixture. Slice the bananas, and fold in the cream mixture together with Grand Marnier. The mixture should be thick.
Spoon into a charlotte mold. Freeze for 2 hours. Unmold on platter and sprinkle with cocoa before serving.